VSAT SATOM TRAINING
Course Introduction
Welcome to the VSAT Installer Training Course. We have put together a comprehensive course that covers all aspects of the VSAT field technician. By the end of the course, we hope you are confident with the installation, operation, maintenance, and fault finding of VSAT satellite equipment.
Here are a few tips to help you during the course:
- Take your time during the lessons.
- Take notes.
- Go back and re-read the lesson if needed.
- If you don’t understand, email satoms support.
- Download the PDF help sheets, software, manuals, spec sheets, and course notes for future reference.
- Enjoy!
Email support@satoms.com if you have any questions during the course. Please remember to leave a course review when you have finished!
Click the ‘Complete’ button below at the end of a lesson to mark it as completed in your user account.
What is VSAT?
VSAT is used in remote areas of the world. A connection to the traditional copper or fiber network is impossible or is used as a backup communication link for mission-critical systems. VSAT is an acronym for Very Small Aperture Terminal and generally refers to a satellite antenna less than 3.8m located at the remote site. VSAT is used for two-way communication for voice and data traffic.
Geostationary communication satellites are positioned one-tenth of the way to the moon (about 36,000 km) and appear stationary when viewed from the Earth’s surface. Many service providers use Geostationary satellites because a fixed antenna can be used and are relatively inexpensive. For Medium Earth Orbit (MEO) satellites, like the O3B network or satellites in an inclined orbit, tracking antennas must be used. These will be covered later in the course.
This video by SES shows how satellites stay in orbit and how VSAT works.
Frequency Bands
Satellite VSAT communication is split into four Radio Frequency (RF) bands within which commercial communication and military satellites operate. These different frequency bands have separate uplink (Transmit) and downlink (Receive) frequencies, require different RF components (LNB and BUC), and are suited to different applications. Commercial satellite service providers use C Band, Ku Band, and occasionally Ka-Band.
C Band
uplink 5.925 – 6.425 GHz
downlink 3.7 – 4.2 GHz
The C band is primarily used for voice and data communications. Because of its weaker power requires a larger antenna, usually above 1.8m (6ft). However, due to the lower frequency range, it performs better under adverse weather conditions like rain.
X Band
uplink 7.9 – 8.4 GHz
downlink 7.25 – 7.75 GHz
The X band is used mainly for military communications and Wideband Global SATCOM (WGS) systems and is not used commercially. With relatively few satellites operating in the X band, there is a wider separation between adjacent satellites, making it ideal for Comms-on-the Move (COTM) applications. This band is less susceptible to rain fade than the Ku Band due to the lower frequency range, resulting in a higher performance level under adverse weather conditions.
Ku Band
uplink 14 – 14.5GHz
downlink 10.9 – 12.75 GHz
Ku (K band Under) band is typically used for commercial VSAT systems. Example uses include offshore oil & gas, maritime, and land-based enterprise connectivity. The antenna sizes, ranging from 0.9m -1.8m (~6ft), are much smaller than the C band because the higher frequency means that higher gain can be achieved with small antenna sizes than C band. Networks in this band are more susceptible to rain fade, especially in tropical areas, and Adaptive Coding Modulation (ACM) is used to prevent these outages.
Ka-Band
uplink 26.5 – 40 GHz
downlink 18 – 20 GHz
The Ka-band (K band Above) is primarily used for two-way consumer broadband and military networks. Ka-band dishes can be much smaller and typically range from 60cm-1.2m (2′ to 4′) in diameter. Transmission power is much greater compared to the C, X, or Ku band beams. This band’s higher frequencies can be more vulnerable to signal quality problems caused by rain fade. Again ACM is used to help rain fade. O3b Network satellite service uses Ka-Band for its connectivity.
Satellite Orbits
A communications satellite is a satellite located in space for telecommunications. There are three altitude classifications for satellite orbits.
LEO – Low Earth Orbit
LEO satellites orbit from 160-2000km above the earth, take approximately 1.5 hrs for a full orbit, and only cover a portion of the earth’s surface, therefore requiring a network or constellation of satellites to provide global, continual coverage. Due to the proximity to Earth, LEO satellites have a lower latency (latency is when a packet is transmitted and the moment it reaches its destination) and require less amplification for transmission.
MEO – Medium Earth Orbit
MEO satellites are located above LEO and below GEO satellites and typically travel in an elliptical orbit over the North and South Pole or in an equatorial orbit. These satellites are traditionally used for GPS navigation systems and are sometimes used by satellite operators for voice and data communications. MEO satellites require a constellation of satellites to provide continuous coverage. Tracking antennas are needed to maintain the link as satellites move in and out of the antenna range.
GEO – Geostationary Orbit
GEO satellites orbit at 35,786 km (22,282 mi) above the equator in the same direction and speed as the earth rotates on its axis. This makes it appear to the earth station as fixed in the sky. Most commercial communications satellites operate in this orbit; however, there is a longer latency due to the earth’s distance.
VSAT Link Terminology
VSAT terminology can often be confusing at first, but it’s really quite simple, and this diagram shows how it relates to the VSAT remote site or the Teleport hub side.
The Uplink is always the link to the satellite, and the downlink is always the link from the satellite irrespective of which side of the link you are, Teleport/Hub or VSAT remote site.
Inbound and Outbound are often referred to as Inroute(s) and Outroute(s). The Outbound is from the teleport hub to the remote VSAT, and the Inbound is the remote VSAT to the teleport hub.
VSAT Latency
A satellite VSAT link’s latency time is a crucial factor when choosing to use a satellite system. It can affect your network’s performance, and some applications experience issues when the latency is too high, not to mention a poor user experience.
Radio Frequency (RF) waves travel at the speed of light, which is a little less than 300,000 km per second (299,792.458 km/s). We can calculate how long a signal will travel from the antenna to the satellite and back down to the distant end of the link. The latency is unaffected by the frequency band of the link.
But not all satellites were created equal. Depending on the type of orbit (i.e., distance) of the satellite, travel time will vary.
VSAT Latency Calculation
We can use the simple speed, distance, and time equation to calculate the time:
speed = distance / time
time = distance / speed
A Geo VSAT Satellite Example
time = 35,786 km / 299,792 km/s
time to satellite = 0.11937 seconds
Therefore, the RF signal’s time to reach the satellite is 0.11937 seconds, but we must come back down again, so it’s really 0.23874 sec or approx. 0.25 sec for a signal (or information, data, packet) to travel across a satellite link. This is called one ‘hop’.
TCP applications (like Pings, internet browsing) require an ‘ack,’ and the Return Trip Time (RTT) of a VSAT link is just under 0.5 seconds or 500 msec.
VSAT Latency Times (PING)
Acceptable latency times over a VSAT link are between 550 – 750 msec. This is more than the 500 msec return trip time due to the data packet processing by the VSAT router, Teleport equipment, etc.
A ping to a device at the other end of the link should be used to get a true reading of the satellite latency, i.e., the distant VSAT modem or hub, Teleport router, or switch. To find a suitable device, you can perform a traceroute to google, showing the route’s connected equipment. Pick a device just after the satellite link. Check the latency times!
If the ping time of the link is greater than 900 msec, we need to consider what other factors might be causing the additional time.
These might include some of the following:
- Traffic congestion – The local traffic is demand is much greater than your VSAT bandwidth.
- Terrestrial links – What route is your traffic taking to reach the destination
- Server location and load – The ping server might be under load and running at max CPU usage
- Distant end equipment
- Oversubscribed VSAT network – the most common cause of VSAT satellite latency, and you need to speak with your satellite provider!
Reducing VSAT Latency
The latency time can be reduced by:
- Using an MEO satellite service like O3B
- Reduce local traffic like software updates – schedule when the office is unattended
- Reduce unwanted traffic on the link like social networks, video downloads, and bittorrents
- Ensure there is adequate network bandwidth available and the service is not oversubscribed.
- Traceroute to google to check where the issue is
- Ping a device at the distant end (Teleport)
VSAT satellite latency should be between 550 and 750msec on a good link.
Rain Fade
Rain fade is the deterioration of the microwave RF signal levels caused by rain precipitation on either end of the satellite VSAT link. Typically, Ku and Ka-band links are affected (frequencies above 11GHz) and can occur at the VSAT remote or the link’s Teleport end. RF energy is absorbed and scattered by the rain droplets and affects the higher frequencies more because of the signal’s wavelength and the size of the rain and the droplet’s shape. Cross polarization isolation will also be reduced.
Line of Sight
Rainstorms many km away from the antenna could still have a detrimental effect, especially if the elevation angle is quite low. The storm is in the line of sight of the antenna and can last for prolonged periods.
VSAT Antenna
Water, snow, and Ice on the antenna and RF feed assembly surface will also cause a decrease in signal levels by approx. 5-15%. A Radome will protect the VSAT electronics from the weather and corrosion, but the water on the Radome’s surface will attenuate the signal when it rains.
Clouds
Clouds are made from water vapor, causing significant loss on high-frequency satellite links. The typical attenuation at Zenith (0° Elevation) is only a few dB below 100 GHz.
Rain Fade Solutions
Possible ways to overcome the effects of rain fade are;
- Site diversity
- Satellite diversity
- Uplink Power Control (UPC)
- Adaptive Coding and Modulation (ACM)
- Hydrophobic coatings on the antenna or Radome
- C-Band VSAT communications
- Link budgets
- Antenna heated blankets
Sun Outage or Solar Transit Events
What is a Sun Outage?
A sun outage (or a solar transit event or sun fade) happens twice a year during the equinox in March and September, when the Sun is directly above the Equator. Each outage lasts for several minutes for a few days and is caused by the satellite passing directly in front of the Sun as the Earth rotates.
The antenna can see the Sun behind the satellite for these short periods, and the LNB receiver is briefly overwhelmed with RF energy (noise) from the Sun. The link’s noise floor will be increased, swamping out the satellite signal for a few minutes. This might cause a total outage of communications or poor throughput depending on the link’s robustness (MODCOD, power). All frequency bands experience increased RF noise during these periods.
Larger dishes (normally at the teleport/hub end) have a narrower, more focused beam and experience shorter outage periods, repeating over a shorter number of days than smaller antennas. But an outage of the hub antenna will affect multiple customers, while an outage at the remote VSAT antenna only affects the link on that antenna.
So, this means each VSAT communication link will experience two sun outages per equinox.
A 2.4m C-band dish will typically see about 11-minute outages daily, recurring at the same time
over the course of a week. The outage time will peak in the middle of the outage cycle.
How to calculate your outages
Several websites can calculate sun outages’ timings, such as this tool, with the antenna locations, frequency band, and size for both antennas.
Adaptive Coding Modulation (ACM)
Adaptive Coding and Modulation (ACM) is a technology that automatically changes the Forward Error Correction (FEC) and modulation utilized on a satellite link to compensate for changes in link conditions to operate at the most efficient coding and modulation scheme available.
Why use ACM?
The changes in link performance are commonly due to atmospheric conditions like rain (rain fade), changes in the RF levels, solar events, noise, or interference. Previously these conditions could result in the link dropping out of the network and making the users angry. ACM prevents these outages and will provide a more robust service, and the link will only drop out under extreme conditions.
- More robust link
- Maximizes link availability
- Required to meet SLA (Service Level Agreements)
- More spectrally efficient for the outbound carrier and remote sites – more data bits per Hz
- MODCOD automatically altered per remote link
- Happy Satellite VSAT users 😊
How does ACM Work?
ACM evaluates current link conditions and throughput requirements through a return channel to determine the ideal modulation and FEC used (MODCOD). This optimizes the bandwidth efficiency for maximum throughput on a remote-by-remote basis in real-time without any intervention from the Network Operations Centre (NOC). The ACM can be limited at a set MODCOD (e.g., 16APSK) to stop any CRC errors if the remote is incapable of receiving these higher-level MODCODs in clear sky conditions.
Linear Polarization
When installing VSAT satellite equipment, you will need to know what polarization is used on the link, and you will have to set up the RF feed assembly correctly.
Cross-Pol (or XPOL) and Co-Pol are used for linear VSAT links.
What do Xpol and Co-Pol mean?
Cross-Pol or XPOL is when the transmit and receive RF signals are separated by 90 degrees. So, when the transmit is vertical, the receive will be horizontal and vice versa.
- Rx vertical and Tx horizontal
- Rx horizontal and Tx vertical
Co-Pol is when the transmit and receive signals are both on the same plane. Transmit and receive are both vertical or horizontal.
- Rx vertical and Tx vertical
- Rx horizontal and Tx horizontal
VSAT Link Commissioning
The satellite operator will normally require you to rotate the RF feed horn to achieve at least 30dB of isolation during the commissioning process. This test is called CPI (Cross Polarisation Isolation). This reduces the interference of your transmit signal on the opposite polarization that might be used by someone else. The NOC (Network Operations Centre) will set up a conference call with the satellite operator. After setting up a Continuous Wave (CW) transmission, you will be asked to move the RF feed horn by 1 or 2-degree steps in one direction and then in the opposite direction. The satellite operator will be looking at both pols on a spectrum analyzer and measuring the max isolation. You may be asked to peak the antenna in azimuth and elevation.
The tech moves the RF feed assembly by hand for static land-based sites and locks it into position after commissioning. Stabilized antennas (SeaTel, Intellian, and SpaceTrack) have an auto-pol motor to move the feed assembly during normal operation. During the commissioning, this has to be disabled and adjusted from the ACU. More details on how to do this are included in the SeaTel and Intellian courses.
With lengthy commissioning testing, some modems will sometimes timeout (safety feature to prevent CW being left on), and you will have to hit ‘Start CW’ again.
After the satellite operator is finished the testing, the results should be recorded for future reference. The remote compression point (1dB point) will normally be checked during this process.
So, achieving good isolation is very important. If this is not done, you will cause interference on the network. The transmit power will be high (reducing the fade margin), lower link MODCOD and the remote site’s inferior performance. It’s best practice to set the polarisation correctly the first time.
RF Equipment
Identifying the correct parts is a massive help. Many people have wasted considerable time and effort only to determine that the incorrect parts have been fitted to the RF feed assembly. If you have inherited equipment from a previous service provider, knowing if it will work quickly will save you time and money.
Cross-Pol combiner the transmit and receive ports are at right angles to each other.
Co-Pol combiner the waveguide ports are in the same direction.
How to calculate and set up the RF feed assembly’s polarization angle to be covered in more detail later in the course.
Circular Polarization
The circular polarization of an electromagnetic wave is a polarization state in which, at each point, the electric field of the wave has a constant magnitude. Still, its direction rotates with time at a steady rate in a plane perpendicular to the wave’s direction.
Circular polarization may be referred to as right-handed or left-handed, clockwise or anti-clockwise, depending on the electric field vector rotates’ direction. Unfortunately, two opposing historical conventions exist, so always check if the polarization is from the signal source or the receiving dish.
Circular polarization can either be RHCP or LHCP.
RHCP – Right Hand Circular Polarization
LHCP – Left Hand Circular Polarization
Link Commissioning
There should be no need to adjust the RF feed assembly’s polarization as the Tx and Rx are circularised on the feed; however, the satellite operator may still want to check the isolation. Cheaper circularises are not precisely circular and more of an oval shape, and you might have to rotate it to achieve isolation.
deciBels (dB)
If you are working in satellite or communications, you will often use dB’s. But what are they?
Bels are too big, so we use deciBels (dB). These are easy ways to multiply large and small numbers. By using dBs, you can add or subtract instead of having to multiply numbers. DBs is a ratio between two levels, and an example is the received signal to noise level (Rx SNR) expressed in dBm (this tells us how strong the signal level is compared to the noise with reference to 1mW).
dB = 10 log [ratio of two power levels]
| deciBel (dB) | Power |
| +10dB | x 10 |
| +3dB | x 2 |
| 0dB | x 1 |
| -3dB | x 0.5 |
| -10dB | x 0.1 |
Question: A 30m RG6 coax has a loss of 3dB. What is the output power if the input is 500mW?
dBW or dBm?
dBW is referenced the power with 1W (Watt)
| dBW | Power |
| 20dBW | 100 Watts |
| 10dBW | 10 Watts |
| 3dBW | 2 Watts |
| 0dBW | 1 Watt |
| -3dBW | 0.5 Watts |
| -30dBW | 0.001 Watts |
dBm is reference the power with 1mW (milliWatt)
| dBm | Power |
| 20dBm | 100 mW |
| 10dBm | 10 mW |
| 3dBm | 2 mW |
| 0dBm | 1 mW |
| -3dBm | 0.5 mW |
| -30dBm | 0.001 mW |
dBm to dBW Conversion
The conversion between dBm and dBW is quite straightforward. 1 Watt is equal to 1000mW, which is an increase of 30dB. So we need to add or subtract 30dB.
dBm = dBW + 30dBW = dBm – 30
Example: Convert 35dBm to dBW
Example: Convert -40dBW to dBm
- Using decibels (dB), you can quickly calculate the overall gain of a communication system by simply adding or subtracting the different components.
DC Voltages
WARNING!
DC Voltages can be supplied by the modem on the Rx and Tx coax connectors. Care must be taken when connecting and disconnecting to prevent equipment damage.
The modem supplies DC voltage for the LNB RX (19V) and BUC TX (24 or 48V) on the coax connector’s center pin.
Care must be taken not to short out this pin when the modem is powered up. Don’t let the center pin touch anything metal if the modem is powered up.
It’s recommended that the modem is powered down when connecting the coax at either end.
RF Safety
Electromagnetic Radiation (EMR)
Electromagnetic Radiation or RF Hazard is the emission of energy in electromagnetic waves through a medium or space.
Cable, Wave Guide, Fibre Optics, Air/Space.
There are two kinds of radiation: Non-ionising and Ionising.
Ionising Radiation
Ionizing radiation consists of subatomic particles or electromagnetic waves that are energetic enough to detach electrons from atoms or molecules, ionizing them. This alters their state and atomic makeup.
This process can produce molecular changes that can damage biological tissue, including effects on DNA and living organisms’ genetic material.
X-rays and Gamma Radiation
Non-Ionising Radiation
Non-ionizing radiation refers to any electromagnetic radiation that does not carry enough energy to ionize atoms or remove an electron from an atom or molecule. Instead of altering the material, the electromagnetic radiation has only sufficient excitation energy. This is noticed as heat or warming.
Visible & Infrared light, VSAT RF
EMR Users
Occupational: An informed and trained user aware of the risks and will take the necessary precautions to minimize those risks, i.e., VSAT field technician.
Non-Occupational: This is a person who does not know the risks involved with emissions from a transmitting device, i.e., clients.
Effects on the Body
95Ghz – exposure of 2sec elevates skin temp to 54 degrees. (Pain Ray)
5.4Ghz – Most of the energy is absorbed in the first 1mm of skin.
1hz to 10Ghz – Penetrate deeper into the body. Cellular injury at 42 degrees. Pain threshold at 45 degrees. Less nerve response past skin layers.
RADHAZ at Work
- Satellite Phones
- Wi-Fi Access Points (WAP)
- Microwave Ovens
- Modems – 1 Watt (L band)
- BUCS – 4 – 20 Watts
- SSPA – 20 – 100Watts
- Ku Band 14.0 – 14.5GHz
- C Band 6.425–6.725GHz
Warning Signs
RF Power
Adding more energy to lower-power radiation can cause similar, if not the same, effects as higher-power radiation.
Variables that change the hazard level:
- Concentration and Amplification
- Exposure time
- Frequency and Energy
Frequencies considered especially dangerous occur where the human body can become resonant at 35 MHz, 70 MHz, 80-100 MHz, 400 MHz, and 1 GHz.
Main Points
- The definition between Ionising and Non-Ionising radiation.
- Non-ionizing Radiation exposure occurs around all communications devices.
- The power of transmission affects the size of the non-ionizing area.
It hurts if you are burnt!
VSAT Glossary of Terms
Here is a list of terms that are used in the VSAT industry. You are not expected to learn every single one but take the time to read through them and download the PDF at the bottom of the page as future reference.
A
Amplitude Modulation – The base-band signal is caused to vary in amplitude or height of the carrier wave to create the desired information content.
Amplifier – A device used to boost the strength of an electrical signal.
Analogue – A form of transmitting information characterized by continuously variable quantities instead of digital transmission, characterized by discrete bits of information in numerical steps.
ADC – Analogue-to-Digital Conversion – A process of converting analog signals to a digital representation. DAC represents the reverse translation.
Antenna – A device for transmitting and receiving radio waves. Depending on their use and operating frequency, antennas can take the form of a single piece of wire, a di-pole, a gride such as a yagi array, a horn, a helix, a parabolic dish.
ACU – Antenna Control Unit -The control unit for antenna tracking controls. Manufacturers include Seatel with their DAC 2202 series, Intellian, Orbit, and SpaceTrack.
ACI – Adjacent Channel Interference – Unwanted electrical interference from signals that are immediately adjacent in frequency to the desired signal. This can arise due to imperfections in the transmission channel and/or equipment.
ACM – Adaptive Coding and Modulation uses an algorithm to dynamically change the coding and modulation scheme based on atmospheric conditions and network configurations.
AES – Advanced Encryption Standard is an encryption standard comprised of three blocks of ciphers AES-128, AES-192, and AES-256
APIU – Antenna Position Indicator – The digital position indicator is normally on or near the ACU.
Aperture – A cross-sectional area of the antenna which is exposed to the satellite signal.
Apogee – The point in an elliptical satellite orbit which is farthest from the surface of the earth. Geosynchronous satellites that maintain circular orbits around the earth are the first launched into highly elliptical orbits with apogees of 22,237 miles or 35,787Km.
AKM – Apogee Kick Motor – A rocket motor fired to circulate orbit and deploy a satellite into geosynchronous orbit.
Assignment Channel – A channel carrying assignment information in the Intelsat TDMA system.
Attenuation – The loss in power of electromagnetic signals between transmission and reception points.
Attitude Control – The orientation of the satellite in relationship to the earth and the sun.
Audio Subcarrier – A carrier between 5MHz and 8MHz containing audio (or voice) information inside a video carrier.
AFC – Automatic Frequency Control – A circuit that automatically controls the frequency of a signal.
AGC – Automatic Gain Control – A circuit that automatically controls an amplifier’s gain so that the output signal level is virtually constant or a varying input signal levels.
AZ/EL Mount – The antenna mount requires two separate adjustments to move from one satellite to another.
Azimuth – The angle of rotation (horizontal) that a ground-based parabolic antenna must be rotated through to a specific satellite in geosynchronous orbit. Can be true or relative azimuth.
B
B-Mac – A method of transmitting and scrambling television signals. In such transmissions, MAC (Multiplexed Analogue Component) signals are time-multiplexed with a digital burst containing digitized sound, video synchronizing, authorization and information.
Backhaul – A terrestrial communications channel linking an earth station to a local switching network or population center.
BO – Backoff – The process of reducing the input and output power levels of a traveling wave tube to obtain a more linear operation.
Band Pass Filter – An active or passive circuit that allows signals within the desired frequency band to pass through but impedes signals outside this passband from getting through.
Bandwidth – A measure of the spectrum (frequency) use or capacity. For example, a voice transmission by telephone requires a bandwidth of about 3000 cycles per second (3 kHz)…read more.
Baseband – The basic direct output signal in an intermediate frequency based obtained directly from a television camera, satellite television receiver, or videotape recorder…read more.
Baud – The rate of data transmission based on the number of signal elements or symbols transmitted per second. Today most digital signals are characterized in bits per second (bps).
Beacon – A low-power and highly stable carrier signal used by earth stations equipped with an automatic (satellite) tracking system. Beacons can be generated on-board the satellite or transmitted from the ground and relayed through the satellite. When generated onboard the satellite, they are also known as satellite or onboard beacons and sometimes carry telemetry signals.
Beam – A unidirectional flow of radio waves concentrated in a particular direction. A term commonly used to refer to an antenna’s radiation pattern by analogy with a light beam. It is most often used to describe the radiation pattern of satellite antennas. The intersection of a satellite beam with the earth’s surface is referred to as the (beam’s) footprint.
Beamwidth – A measure of the ability of an antenna to focus signal energy towards a particular direction in space (e.g., towards the satellite for a ground-based transmitting antenna) or to collect signal energy from a particular direction in space (e.g., from the satellite for a ground-based receiving antenna). The beamwidth is measured in a plane containing the direction of maximum signal strength. It is usually expressed as the angular separation between the two directions in which the signal strength is reduced to one-half of the maximum value (the -3 dB half-power points).
Bel – The unit of which the Decibel (dB) is one-tenth.
Bird – Slang for a communication satellite located in geostationary orbit.
Bit – A single digital unit of information (e.g., 1 or 0).
BER – Bit Error Rate – The fraction of a sequence of message bits that are in error. A bit error rate of 10-6 means an average of one error per million bits.
Bit Rate – The speed of a digital transmission, measured in bits per second (bps).
BNC Connector – A twist-lock coaxial connector commonly used on commercial video equipment and some satellite receiver brands. It can be 50 or 75Ω, and one way to tell which type you have is to look at the size of the center pin on the BNC connector, or it may be printed on the cable’s outer sheath.
BDC – Block Down Converter – A device used to convert the C or Ku band signals down to UHF or lower frequencies (1 GHz and lower).
BUC – Block Up-Converter – Earth station transmitter combining signal up-conversion and power amplification in a single unit, normally located directly at the antenna input or close to it. Typically converts the L band signal from the satellite modem to C or Ku band frequencies.
Byte – A sequence of bits processed as one unit of information. A byte is a digital “word” normally consisting of eight bits (e.g., 11110000).
C
C Band – This is the band of frequencies between 4 to 8 GHz with the 6 GHz and 4 GHz band used for satellite communication. Specifically, the 3.7 to 4.2 GHz satellite communication is used for the downlink frequencies in tandem with the 5.925 to 6.425 GHz band that serves as the uplink—satellite Frequency bands in detail.
C/I – Carrier to Interference Ratio – Carrier-to-Interference-Ratio. A measure of the quality of a signal at the receiver input. It is the ratio of the carrier’s power to the power of interference arising from human-made sources, measured within a specified bandwidth (usually the modulated carrier’s bandwidth). It is usually expressed in decibels. The higher the ratio, the better quality of the received signal.
C/N – Carrier to Noise Ratio -Carrier-to-Noise-Ratio. A measure of the quality of a modulated carrier at the receiver input. The ratio of the carrier’s power to the power of the noise introduced in the transmission medium, measured within a specified bandwidth (usually the modulated carrier’s bandwidth). It is usually expressed in decibels. The higher the ratio, the better quality of the received carrier.
C/T – Carrier to Temperature Ratio – The ratio normally used to quantify noise contributions.
Carrier – The basic radio, television, or telephony center of frequency transmit signal. The carrier in an analog signal is modulated by manipulating its amplitude (make it louder or softer) or its frequency (shifting it up or down) with the incoming signal. Satellite carriers operating in the analog mode are usually frequency modulated.
Carrier Frequency – The main frequency on which a voice, data, or video signal is sent. Microwave and satellite communications transmitters operate in the band from 1 to 14GHz (a GHz is one billion cycles per second).
Cassegrain Antenna – The antenna principle that utilizes a sub-reflector at the focal point reflects energy to or from a feed located at the main reflector’s apex.
CDMA – Code Division Multiple Access – Code Division Multiple Access refers to a multiple-access scheme where stations use spread-spectrum modulations and orthogonal codes to avoid interfering with another.
Channel – A band of radio frequencies assigned for a particular purpose, usually establishing one complete communication link or a path for an electrical signal. This term is often used interchangeably with Transponder, but in general, the channel bandwidth is less than the transponder bandwidth.
CinC – Carrier in Carrier -This is one of the latest techniques the satellite industry has adopted to enable customers to save on bandwidth costs. It allows a full-duplex satellite link to be allocated the same transponder space as a single carrier using Applied Signals patented technology – Adaptive Cancellation – to place carriers directly on top of one another in terms of frequency. Read More…
Circular Polarisation – A circularly-polarised wave. The electric field vector, observed in any fixed plane normal to the direction of propagation, rotates with time and traces a circle in the observation plane. Unlike linear polarization, circular polarisation does not require the alignment of earth station and satellite antennas with the radio waves’ polarization.
Clamp – A video processing circuit that removes the energy dispersal signal component from the video waveform.
Clarke Orbit – The circular orbit at approximately 35,800 km above the equator. The satellites travel simultaneously as the earth’s rotation (Geostationary Orbit) and thus appear to be stationary to an observer on Earth. Named after Arthur C. Clarke, who first postulated the idea of geostationary communication satellites.
Clear Sky – A term describing the weather conditions encountered at the terrestrial end of an earth-space path of a satellite communication link. It is used to describe the condition where radio waves’ attenuation caused by precipitation (rain, snow, sleet, dew, etc.) is lowest (cloud-free sky and good visibility).
C/N – Carrier to Noise Ratio – is measured either at the Radio Frequency (RF) or Intermediate Frequency (IF).
Coaxial Cable – Commonly shortened to Coax. A cable consisting of an inner insulated core of stranded or solid wire surrounded by an insulated flexible wire braid. Used principally as a transmission line for radio frequency signals with low loss. Often referred to as screened cable because the outer braid screens the inner conductor from electrical interference. How To: Terminate an F-type connector on a coax cable.
Codec – Coder/Decoder system for digital transmission.
C0-Location – Ability of multiple satellites to share the same approximate geostationary orbital assignment, frequently since different frequency bands are used.
Colour Subcarrier -A sub-carrier that is added to the main video signal to convey the color information. In NTSC systems, the color sun-carrier is centered on a frequency of 3.579545MHz, referenced to the main video carrier.
Common Carrier – Any organization which operates communications circuits used by other people. Common carriers include telephone companies as well as the owners of satellites, Comsat, Direct Net, AT&T, and others.
Coverage – The geographical area in which satellite signals can be transmitted or received with sufficient quality when using appropriately sized earth stations. Satellite coverage is usually communicated in the form of footprints displaying satellite G/T, EIRP, or other quantities, such as the antenna size required for good quality reception of a particular service.
Cross Modulation – A form of signal distortion in which modulation from one or more RF carrier(s) is imposed on another carrier.
C/T – Carrier to Noise Temperature Ratio.
D
E
F
G
Gain – A measure of amplification expressed in dB
GEO – Geostationary Earth Orbit satellites orbit at 35,786 km (22,282 mi) above the equator in the same direction and speed as the earth rotates on its axis, making them appear as fixed in the sky
GSM – Global System for Mobile communications is a standard for digital wireless communications to mobile phones
GQoS – Group Quality of Service is a bandwidth allocation and prioritization algorithm that allows for countless possibilities of quality of service levels, bandwidth management, and traffic prioritization
G/T – A figure of merit of an antenna and low noise amplifier combination expressed in dB. “G” is the gain of the system, and “T” is the noise temperature. The higher the G/T, the better the system
Guard Band – Transmission carriers are separated on a transponder by spacing them several kilohertz apart. This unused space serves to prevent the adjacent transmission carriers from interfering with each other.
GUI – Graphical User Interface is a type of user interface that allows users to interact with electronic devices using images rather than text commands
H
HNO – Host Network Operator is a network operator who leases out hub space to smaller service providers
HTS -High Throughput Satellites is a classification for communications satellites that provide at least twice, though usually by a factor of 20 or more, the total throughput of a classic Fixed Satellite Service (FSS) satellite for the same amount of allocated orbital spectrum, thus reducing cost-per-bit
HTTP – HyperText Transfer Protocol is an application-level protocol used to request and transfer objects across the web
Hub – Satellite network equipment that controls the satellite bandwidth allocation, often located at a teleport. It usually consists of a chassis and other equipment connected to terrestrial networks.
I
IDU – Indoor Unit is network equipment typically located inside a building that consists of a modem and router (or hub if it is inside a teleport) connected to the corporate LAN or terrestrial infrastructure
IP – Internet Protocol is a protocol used for data communication across a packet-switched network. Typically used with TCP, a higher-level protocol.
ISO – International Organization for Standardization is a standard-setting body composed of multiple national standards organizations
ISP – Internet Service Provider is a company that offers Internet access to customers
ITU – International Telecommunication Union is a United Nations organization helping governments and private organizations coordinate global telecommunications usage
Inbound – Transmission of a signal to the satellite. A network is typically referred to as the transmission from the remote router to a satellite to a hub.
Inroute – See Inbound
J
K
Ka-Band – Frequency band with uplink 26.5‐40GHz; downlink 18‐20 GHz. This band was previously known for consumer broadband applications and is now widening to enterprise and military use.
Kbps – Kilobits per second. This refers to the transmission speed of 1,024 bits per second is 1kbps.
Ku Band – Frequency band with uplink 14 GHz; downlink 10.9‐12.75 GHz, with more powerful transmission from the satellite more susceptible to rain fade than C-Band. Satellite Frequency bands in detail.
L
L-Band – The frequency range from 500 MHz to 1.5 GHz. It is also used to refer to the 950 MHz to 1450 MHz used for mobile communications.
LDPC – Low-Density Parity Check is a forward error correction code that is currently the most efficient scheme used with DVB-S2
LEO – Low Earth Orbit satellites orbit from 160 to 2000 km above the earth and take approximately 1.5 hrs for a full orbit and only cover a portion of the earth’s surface
LHCP – Left Hand Circular Polarisation.
LAN – Local Area Network is a computer network that covers a small physical area
Leased Line – A dedicated circuit typically supplied by the communications company.
LNA – Low Noise Amplifier – This is a preamplifier between the antenna and the earth station receiver. It must be located near the antenna as possible and is usually connected to the antenna receive port for maximum effectiveness.
LNB – Low-Noise Block – A low-noise block (or LNB) is the receiving device mounted on the feed of satellite dishes, which collects the dish’s radio waves. LNB Page.
LNC– Low Noise Converter
M
MEO – MEO satellite orbits are located above LEO and below GEO satellites and typically travel in an elliptical orbit over the North and South Pole or in an equatorial orbit
Mesh Network – Topology whereby a remote VSAT location communicates with another remote location without routing through the hub
MF‐TDMA – Multiple-Frequency Time-Division Multiple-Access is a broadband access method where different data streams are put into different slots that are separated by both frequency and time
MIR – Maximum Information Rate is the theoretical maximum amount of bandwidth available to a subscriber, typically expressed in kilobits per second
Modem – A piece of network equipment containing a modulator and demodulator for receiving or transmitting satellite signals
Modulation – The encoding of a carrier wave by amplitude or frequency or phase
Modulator – A device that modulates a carrier
Multicast – Multicast is a subset of broadcast whereby the signal can be sent to many sites within a defined group, but not necessarily to all sites in that group
Multiplexing – sending multiple signals or streams of information on a carrier simultaneously transmitting on a single signal
N
Narrowband – Refers to satellite communications of 128 kbps or lower (per Frost & Sullivan)
NOC – Network Operations Center is a centralized location where control over the operation of a network is managed and monitored
Noise – Any unwanted and unmodulated energy that is always present to some extent within any signal
NMS – Network Management System is the hardware and software that monitors and controls a satellite network
NTP – Network Time Protocol is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks
O
ODU – Outdoor Unit – An ODU is the equipment located outside of a building and includes the satellite antenna or dish, a low noise block converter (LNB), and a block-up-converter (BUC). The LNB converter amplifies the received signal and down-converts the satellite signal to the L band (950 MHz to 1550 MHz). The BUC amplifies the uplink transmission when the antenna is transmitting.
OSS – Operational Support System refers to network systems dealing with the telecom network itself, supporting processes such as maintaining network inventory, provisioning services, configuring network components, and managing defaults
Outbound – Transmission of a signal from the satellite to an antenna. A network is typically referred to as the transmission from the hub to a satellite to a remote router.
P
PBX – A Private Branch Exchange is a telephone exchange that connects a private enterprise or organization to the public switched telephone network
PCMA – The Paired Carrier Multiple Access (PCMA) Hub Canceller is a satellite signal canceller that maximizes the capacity of satellite networks by using ViaSat’s patented PCMA technology to reduce satellite bandwidth as much as 50 percent
PDU – Power Distribution Unit is a device fitted with multiple outlets designed to distribute electric power, especially to racks of computers and networking equipment located with the data center
Phase-Locked Loop (PLL) – A type of electronic circuit used in a wide variety of telecommunications equipment. PLL circuits generate an output signal which is phase-locked to an input signal, leading to more stable output frequencies that are less affected by noise and temperature. For example, the frequency output from a PLL LNB will be more stable than the output from a regular LNB.
Polarization – A technique used by satellite operators to reuse the satellite transponder frequencies when transmitting these signals to Earth. Two methods are possible: linear and circular. To successfully receive and decode these signals on earth, the antenna must be outfitted with a properly polarized linear or circular feedhorn to select the desired signals.
PSK – Phase Shift Key is a digital modulation scheme that changes the phase of the carrier wave
PSTN – Public Switched Telephone Network is an international network for public circuit-switched voice telephony
Q
QEF – Quasi Error Free is a condition where the transmission system or storage medium used to transfer a signal has a relatively low bit error rate
QoS – Quality of Service provides priority and guarantees a certain level of network response time and other performance factors for each application and user
QPSK – Quadrature Phase Key Shifting is a modulation scheme that uses four phases
R
Rain Fade – Decrease of satellite signal strength due to rainfall. This occurs typically at Ku and Ka-Band frequencies due to its increased sensitivity to noise temperature.
RF – Radio Frequency is the electromagnetic frequencies for wireless transmission that is above the audio range and below infrared light; typically used in the satellite industry in the context of RF equipment (antenna system and BUC)
RIP – Routing Information Protocol is a dynamic routing protocol used in the local area and wide area networks
Router – A device connected to the modem and the antenna on one side and the computers and other LAN devices on the other side. It forwards IP packets based on network layer information and enables applications such as VoIP, Video, and data.
S
Satellite – Communications satellites orbit the earth and transmit and receive radio signals from earth stations.
SCADA – Supervisory Control and Data Acquisition is the system that monitors and controls industrial or facility-based remote devices
Single‐Channel‐Per‐Carrier (SCPC) – A satellite access method that dedicates one channel to each remote site, sometimes used for very high-capacity links. See also TDMA
Signal To Noise Ratio (S/N) – The ratio of the signal power and noise power. The higher the number, the better the quality.
Single Hop – Transmission of information from one remote site to another antenna. Typically it describes the path between two remote stations in a mesh network. Single hop occurs when the transmission is passed from one remote directly to another mote without having to go to the hub (double hop)
SNG – Satellite newsgathering is typically done from a transportable unit (truck or mobile entity) to transmit video and voice feeds back to the studios
Space Segment – The portion of the satellite bandwidth and transmission power assigned to the communication network
Spot Beam – A spot beam is a satellite signal covering a concentrated geographic area, so only antennas in that area will receive the signal.
Spread Spectrum – Eliminates adjacent satellite interference by spreading the signal over the available bandwidth to enable tiny antennas or phased array antennas in mobile operations.
Star Network – Topology whereby a remote VSAT location communicates with another remote location by routing through the hub
Symbol Rate – Symbol Rate (SR) is the number of symbol changes per second made to the signal according to the modulation coding method (ModCod) used. Each symbol represents 1, 2, 3, 4, etc., bits of transmission rate data. Symbol Rate Calculation Formula
T
TCP – Transmission Control Protocol is a core Internet protocol that is a higher-level protocol often combined with IP
TDM – Time Division Multiplex is a type of digital multiplexing in which two or more signals are transferred simultaneously as sub-channels in one communication channel but are physically taking turns on the channel through several recurrent timeslots of fixed length
TDMA – Time Division Multiple Access is a channel access method that allows applications or users to share the same frequency by dividing the full bandwidth into specific timeslots
Transponder – Receives outbound signal at the satellite and amplifies it before retransmitting it to an earth station.
TRANSEC – Transmission Security secures VSAT transmissions with encryption to prevent interception and exploitation
U
Unicast – transmission between a single sender and a single receiver over a network. Contrast with Multicast, which is the transmission between a single sender and multiple receivers.
Uplink – Transmission of a signal from the remote router to a satellite to a hub
V
VLAN – Virtual LAN is a group of hosts that simulates a LAN although they are not located locally on the same network switch
VNO – Virtual Network Operators lease hub space from HNOs while keeping complete control of their network and remotes.
VSAT – Very Small Aperture Terminal is an antenna that is typically less than 3 meters in diameter
Vertical Polarisation – Type of linear polarisation where the electric field is approximately aligned with the local vertical plane at an on-ground transmission or reception point
W
WAN – Wide Area Network is a computer network that covers a broad area that connects multiple remote locations
WGS – Wideband Global Satcom is a satellite communication system used by the U.S. Department of Defense
X
X band -uplink 7.9- 8.4 GHz, downlink 7.25 – 7.75 GHz
The X band is used mainly for military communications and Wideband Global SATCOM (WGS) systems. With relatively few satellites in orbit in this band, there is a wider separation between adjacent satellites, making it ideal for Comms-on-the Move (COTM) applications. This band is less susceptible to rain fade than the Ku Band due to the lower frequency range, resulting in a higher performance level under adverse weather conditions. Satellite Frequency bands in detail.
X-Polarisation – A more precise definition of horizontal linear polarisation. X-polarisation is defined with respect to a particular direction from the satellite towards the earth, allowing precise calculation of the polarization alignment angle for any given geographic location.
Y
Y-Polarisation – A more precise definition of vertical linear polarisation. Y-polarisation is defined with respect to a particular direction from the satellite towards the earth, allowing precise calculation of the polarization alignment angle for any given geographic location.
Z
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